Saints Row 2, the sequel that was perfect in every way, expanding on the world of Saints Row 1, with new gangs, new vehicles, new weapons, more customisation options, a bigger city, an amazingly satisfying story and best of all, the addition of 2 player CO OP!
SR2 is probably one of the best examples of a cooperative sandbox game there is! In a game where players get to complete missions any way they see fit, 2 player only adds to the game! Why not run a muck in the city together? Sample hitting each other with every item you can get your hands on in the game! Race each other to destinations, fly under bridges with helicopter support standing by to revive you after trying something stupid! It's all there! It's all brilliant!
Not to mention the story line in SR2 offers some of the most satisfying moments in video game history! (Try and tell me you didn't enjoy every second of the Ronin story!) With Johnny Gat back and as funny as ever!
This game has aged surprisingly well given how old it is, the only place it feels a little dated is in the length of the levels...they just kind of cut off right when you think there should be a massive gun fight or something. But that's OK! It's a sandbox! Have the gun fight once you're done!